Inhibited treating acid

ABSTRACT

The present invention is directed to an inhibited treating acid for use in contact with ferrous surfaces at temperatures of from about 150*F to about 450*F.

United States Patent Keeney et al. 1 Nov. 20, 1973 [541 INHIBITED TREATING ACID 3,507,795 4/1970 Gardner 252/ 147 X 3,658,720 4/1972 M D 1 t a]... 252 148 X [75] Inventors Keeney; JohnsmlJr" 3,686,129 8/1972 252 147 both of Duncan Okla- 3,705,106 12 1972 Muzyczko et a1.. 134/3 x 7 Assignee: Halliburton Company Duncan 2,049,517 8/1936 Saukartis 252/149 X 0k] 3,249,547 5/1966 Flsher 2l/2.7 X 3,260,673 7/1966 Fisher 252/389 X 22 il Oct 2 1970 2,559,580 7/1951 Alexander... 252/389 X 2,377,966 6/1945 Reed 23/150 1 1 pp 86,978 2,567,156 9/1951 Malowan 252/389 x 52 us. (:1 21/2.7 R, 134/3, 134/41, Primary Examiner-Barry Birchman 252/147, 252/148, 252/389 Attorney-John H. Tregoning [51] Int. Cl. C23f 11/04, C23g 1/04, C23g 1/06 [58] Field of Search 2l/2.5, 2.7;

252/389, 394, 147, 148; 134/3, 41, 42 [57] ABSTRACT The present invention is directed to an inhibited treat- [56] References Cited ing acid for use in contact with ferrous surfaces at UNITED STATES PATENTS temperatures of from about 150F to about 450F.

3,146,208 8/1964 Fisher 252 148 17 Claims No Drawings 3,243,379 3/1966 Claytonm. 252/148 3,404,094 10/1968 Keeney 252/148 INHIBITED TREATING ACID The present invention relates generally to the field of protecting ferrous metals from the corrosive effects of acids, and has particular application in situations where the temperature at which the metal and acid are in contact is between about 150F and 450F.

Ferrous metals are sought to be protected from the corrosive effects of acids when, for example, acids are used to clean ferrous metal forms or when acids are passed through ferrous metal conduits enroute to treat another substance, such as the treatment of a subterranean formation with acid by passing the acid through an oil well casing enroute to the formation. Many various types of compositions have been used to reduce the corrosive effects of acids on ferrous metals. Nitrogen compositions and acetylenic compositions have been found to be useful in most cases to inhibit the corrosive effects of acids on ferrous metals. Typical acid corrosion inhibitors are those taught in US. Pat. Nos. 3,514,410, 3,404,094, 3,107,221 and 2,993,863. A particular failing of these acid corrosion inhibitors of the prior art is that their effectiveness is greatly reduced in the presence of temperatures greater than about 200F.

Various metals and metal ions have been used in the past as acid corrosion inhibitors but with unsatisfactory results at temperatures greater than about 200F. For example, copper has been added to the acid as cuprous oxide and as cuprous chloride. However, only limited improvement in corrosion inhibition at high temperatures has been noted. Arsenic has also been used as an acid corrosion inhibitor. However, it has been found that arsenic will not provide high temperature acid corrosion inhibition in acid strengths above about 17 percent by weight of acid in water. In addition, arsenic has been known to produce poisonous arsine gas when used as an acid corrosion inhibitor. When arsenic is used as an inhibitor in acid for treating oil wells, any arsenic which becomes mixed with oil produced from said well has been found to have an adverse effect on the catalysts used in refineries where the oil is processed.

Tin and iodine have been used as tin chloride and potassium iodide in efforts to intensify the effects of acid corrosion inhibitors. However, only limited success has been obtained.

The present invention provides an inhibited treating acid for use at temperatures of from about 150F to about 450F where acid corrosion to metals in contact with said inhibited treating acid is sought to be limited to not more than about 0.10 lbs./ft. which comprises a treating acid selected from the group consisting of organic and inorganic acids and mixtures thereof, an acid corrosion inhibitor selected from the group consisting of nitrogen compounds, acetylenic compounds and mixtures thereof, and cuprous iodide present in a concentration of from about ppm (parts per million) at temperatures of from about 150F to about 25,000 ppm at temperatures of about 450F.

In the preferred form of the invention cuprous iodide is combined with an acid which may be hydrochloric acid, sulfuric acid, hydrofluoric acid, acetic acid or mixtures thereof (hereinafter referred to as treating acid), and an acid corrosion inhibitor which may be an acetylenic compound, a nitrogen compound, or a mixture thereof (hereinafter referred to as acid corrosion inhibitor") to produce a highly inhibited treating acid which is especially useful at temperatures of from about F to about 450F.

Cuprous iodide is combined with the treating acid and acid corrosion inhibitor in amounts sufiicient to prevent corrosion to ferrous metal surfaces from exceeding about 0.10 lbs/ft. during any period of contact between the ferrous metal surface and the treating acid-acid corrosion inhibitor-cuprous iodide mixture (hereinafter referred to as inhibited treating acid"). Y

Cuprous iodide, when placed in solution, has a Cu+ to 1- ratio of about 1:2. That is about 2,000 ppm cuprous iodide placed in solution will yield about 668 ppm Cu+ ions and about 1,332 ppm 1- ions. Experimentation has disclosed that if exactly the above ratio of Cu+ ions and 1- ions are provided from soluble salts for an in situ formation of cuprous iodide, the degree of corrosion inhibition provided thereby is not as great as expected from cuprous iodide. However, it has been found that an excess of from about 5 percent to about 15 percent of the compound supplying the 1- ions will provide the desired degree of inhibition.

It has been discovered that the cuprous iodide produced in situ by reactants which also form free iodine will operate in the inventive manner, but show a smaller degree of improvement. Therefore, the most preferred reactants for producing cuprous iodide in situ are those which do not produce free iodine. Therefore, preferred compounds for forming cuprous iodide in situ (in the treating acid either before or after said acid is combined with said acid corrosion inhibitor) are acid soluble salts of iodine and acid soluble salts of copper which, upon reacting, do not form free iodine. Examples of such salts are potassium iodide and sodium iodide as a source of iodide ions and cuprous chloride and cuprous oxide as a source of copper ions. Examples of other salts which may be used as a source of copper ions are cupric chloride and cupric sulfate; however, these are not preferred salts because they form free iodine when reacted with iodine salts.

To be effective, the cuprous iodide must be combined with the treating acid-acid corrosion inhibitor mixture in concentrations of from about 25 ppm by weight of said mixture at temperatures of about 150F to about 25 ,000 ppm by weight of said mixture at temperatures of about 450F. The amount of cuprous iodide required to produce the desired degree of inhibition (less than about 0.10 lbs/ft?) varies with the temperature of the intensified treating acid and with the efficiency of the acid corrosion inhibitor used. Most relatively inefficient acid corrosion inhibitors, when mixed with the treating acid, require about 25,000 ppm cuprous iodide at temperatures of about 450F to prevent corrosion to ferrous surfaces in contact with said inhibited treating acid from exceeding 0.10 lbs./ft.. If less than about 25,000 ppm cuprous iodide is present at temperatures of about 450F, the corrosion to ferrous metals in contact with the intensified treating acid will exceed 0.10 lbs/ft. However, it is to be understood that smaller concentrations of cuprous iodide may be effective in preventing corrosion to ferrous surfaces from exceeding 0.10 lbs./ft. at 450F if a relatively more efficient acid corrosion inhibitor is combined with the treating acid. If less than 25 ppm cuprous iodide is combined with the treating acid and the acid corrosion inhibitor at about 150F, no intensification of the acid corrosion inhibition of the treating acid-acid corrosion inhibitor mixture is noted.

The acid corrosion inhibitor to be combined with the treating acid and the cuprous iodide can be an acetylenic compound, a nitrogen compound or a mixture thereof. It may be an inhibitor taught in U.S. Pat. Nos. 3,514,410, 3,404,094, 3,107,221, 2,993,863 and 3,382,179.

Some examples of acetylenic compounds which may be employed in the present invention are hexynol, dimethyl hexynol, dimethyl hexynediol, dimethyl hexanediol, dimethyl oxtynediol, methyl butynol, methyl pentynol, ethynyl cyclohexanol, 2-ethyl hexanol, phenyl butynol, and ditertiary acetylenic glycol.

Other acetylenic compounds which can be employed in accordance with the present invention are for example, butynediol, l-ethynylcyclohexanol, 3-methyl-l nonyn-3-ol, 2-methyl-3-butyn-2-ol; also l-propyn-3-ol, 1-butyn-3-ol, l-pentyn-3-ol, l-heptyn-3-ol, 1-octyn-3- ol, 1-nonyn-3-ol, 1-decyn-3-ol, l-(2,4,6,-trimethyl-3 cyclohexenyl)-3-propyne l-ol, and in general acetylenic compounds having the general formula wherein R is H, alkyl, phenyl, substituted phenyl or hydroxy-alkyl radical, and the alpha Rs may be joined together to form a cyclohexyl ring.

Acetylenic sulfides having the general formula can also be employed in the present invention in lieu of acetylenic alcohols. Examples of these are dipropargyl sulfide, bis (l-rnethyl-2-propynyl) sulfide and his (2-ethynyl-2-propyl sulfide.

The nitrogen or ammonia compounds that can be employed in accordance with the present invention are those amines such as mono, di and trialkyl amines having from two to six carbon atoms in each alkyl moiety as well as the six membered N-heterocyclic amines, for example, alkyl pyridines and mixtures thereof. This includes such amines as ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, tripropylamine, mono, di and tributylamine, mono, di and tripentylamine, mono, di and trihexylamine and isomers of these such as isopropylamine, tertiarybutylamine, etc. This also includes alkyl pyridines having from one to five nuclear alkyl substituents per pyridine moiety, said alkyl substituents having from one to 12 carbon atoms and preferably those having an average of six carbon atoms per pyridine moiety, such as a mixture of high boiling tertiary-nitrogen heterocyclic compounds such as HAP (High Alkyl Pyridines), Reilly -20 base and Alkyl Pyridines HB.

The acid corrosion inhibitor should be present in the inhibited treating acid in a concentration of from about 0.1 percent at temperatures of about 150F to about 2.5 percent at temperatures of about 450F by volume of inhibited treating acid. Acid corrosion inhibitor concentrations greater than about 2.5 percent by volume of inhibited treating acid do not produce an increase in acid corrosion inhibition at any temperature, and concentrations of acid corrosion inhibitor of less than 0.1 percent by volume of inhibited treating acid results in little or no acid corrosion inhibition at temperatures of about 150F or greater.

Examples of commercially available acid corrosion inhibitors useful in the inhibited treating acid are HAI- 50 and Blend-57 (Halliburton Services, Inc.), Dowel]- Al 10 (Dow Chemical Co.), and Wellaid-2l l (AMOCO brand).

The treating acid useful in the present invention may be hydrochloric acid, hydrofluoric acid, sulfuric acid and mixtures thereof. The acid should be present in strengths of from about pH 6.5 to about 35 percent by weight of acid in water. Acids weaker than those having a pH of 6.5 do not perform as treating acids, and those having an acid strength greater than 35 percent by weight of acid in water are too corrosive to be used as treating acids.

Corrosion loss to metal surfaces treated with acids is generally measured in pounds of metal taken into solution by the treating acid per square foot of metal surface exposed to said acid. An acid corrosion loss of about 0.05 lbs./ft. is generally thought of as being an acceptable loss during an acid treatment, although slightly higher corrosion losses are sometimes considered acceptable at temperatures of about 400F or greater, if the corrosion is uniform. Heretofore, metal surfaces could not generally be exposed to treating acids at temperatures above about 150F without exceeding an acid corrosion loss of about 0.05 lbs./ft. Corrosion losses in the presence of treating acids tend to rise with the temperature of said acid. Acid corrosion inhibitors used with the treating acids are not able to maintain acid corrosion losses within the above described acceptable limits at temperatures up to about 450F.

For example, an API Type N- metal surface treated with 30 percent hydrochloric acid containing Blend-57 acid corrosion inhibitor in a concentration of about 2.0 percent by volume of the hydrochloric acid demonstrated a corrosion loss of about 0.77 lbs./ft. after about two hours contact at about 300F. between the treating acid-acid corrosion inhibitor mixture. This is well above the acceptable limit of 0.05 lbs./ft. However, when the same concentrations of treating acid and acid corrosion inhibitor are combined with 1 1,000 ppm cuprous iodide to form the inhibited treating acid of the present invention, the acid corrosion loss experienced under the same contact conditions is about 0.04 lbs./ft. safely within the acceptable acid corrosion limit.

Under the same conditions, except at a contact temperature of about 400F and a treating acid strength of 15 percent, an API Type N-80 metal surface will dissolve when exposed to the treating acid-acid corrosion inhibitor mixture. However, when exposed to the inhibited treating acid of the present invention containing about 15,000 ppm cuprous iodide, the acid corrosion loss is held to about 0.062 lbs./ft.

Experiments have also shown that corrosion can be significantly reduced by combining cuprous iodide with treating acid-acid corrosion inhibitor mixtures comprising an acid other than hydrochloric acid. For example, at 200F with a contact time of 6 hours a 10 percent sulfuric acid-acid corrosion inhibitor mixture will produce a 0.07 lbs./ft. corrosion loss on API Type N-80 metal. The addition of 500 ppm cuprous iodide to said treating acid will reduce the corrosion to 0.021 lbs./ft. Under similar conditions the addition of 500 ppm cuprous iodide will reduce the corrosion caused by 10 percent acetic acid and an acid corrosion inhibitor from about 0.0016 to about 0.0014 lbs./ft. In similar mixtures, the addition of 500 ppm cuprous iodide reduces the corrosion caused by a 15% hydrochloricacetic acid blend from about 0.010 to about 0.005 ]bs./ft. a 12% hydrochloric-3% hydrofluoric blend from about 0.019 to about 0.004 lbs./ft.

The effectiveness of weak acid corrosion inhibitors such as ethyl octynol can be dramatically improved by the addition of cuprous iodide. For example, a mixture containing percent hydrochloric acid and ethyl octynol in a concentration of about 0.3 percent by weight of acid will produce a corrosion loss of about 0.38 lbs/ft? to the surface of API Type N-80 metal during a contact time of 6 hours at 200F. The addition of 500 ppm cuprous iodide, forming an inhibited treating acid, will reduce the corrosion to about 0.044 lbs./ft.

Cuprous iodide has been found to produce an acceptable acid corrosion reduction when combined with treating acid-acid corrosion inhibitor mixtures at temperatures above about 150F, where other compounds containing copper and iodine have not been effective. For example, in a mixture of acid corrosion inhibitor and 15 percent hydrochloric acid the addition of 7,000 ppm cuprous iodide prevented the acid corrosion from exceeding about 0.013 lbs/ft. on API Type N-80 metal surface after a contact time of two hours at 350F. The addition to the same mixture of 7 ,000 ppm ferrous iodide resulted in a corrosion loss of about 0.182 lbs./ft. the addition of iodopropane, about 0.236 lbs./ft. the addition of iodomethane, about 0.320 lbs./ft. the addition of cupric sulfide, about 0.226 lbs./ft. and the addition of cuprous sulfide, about 0.241 lbs./ft. It is clear, then, that the combination of cuprous iodide with an acid corrosion inhibitor and a treating acid produces a surprising improvement in the protection of metal surfaces against acid corrosion.

It has also been discovered that cuprous iodide will operate as an acid corrosion inhibitor at temperatures of less than about 150F. That is, cuprous iodide may be added to a treating acid or formed in situ in the treating acid at concentrations of from about 50 ppm to about 3,000 ppm to reduce acid corrosion to a metal surface in contact with the treating acid. If less than about 50 ppm cuprous iodide is combined with the treating acid, no significant decrease in acid corrosion is noted. If more than about 3,000 ppm cuprous iodide is added to the treating acid, no additional improvement in the acid corrosion inhibition is found.

For example, when API Type J-55 steel is exposed to 15 percent hydrochloric acid at a temperature of about 150F for about two hours, a corrosion loss to the steel surface can be measured at about 0.037 lbs/ft. However, when 250 ppm cuprous iodide is added to the treating acid the corrosion is reduced to about 0.012 lbs./ft. and when 3,000 ppm cuprous iodide is added to the treating acid the corrosion is reduced to about 0.007 lbs./ft.

The inhibited treating acid herein described may be used to treat subterranean formations having a temperature of between about 150F and about 450F while preventing corrosion to the casing or tubing used to transmit the inhibited treating acid to said formations from exceeding about 0.10 lbs./ft. In such an acid treatment of said subterranean formations, especially of oil or gas wells, the inhibited treating acid may be mixed in any sequence. That is, the cuprous iodide may be added to the treating acid which is then combined with the acid corrosion inhibitor, or the cuprous iodide may be added first to the acid corrosion inhibitor which is later combined with the acid. The cuprous iodide may be added to a mixture of treating acid and acid 5 corrosion inhibitor, the order of mixing not being limited to any particular sequence. The cuprous iodide may also be formed in situ in the treating acid or in the treating acid after it has been combined with the acid corrosion inhibitor.

The inhibited treating acid is then pumped through the well tubing or casing into said formation and left in contact with said formation until the desired effect on the formation has been obtained. The inhibited treating acid is then removed from said formation.

Tests have also revealed that cuprous iodide operates to extend the life of the commonly known acid corrosion inhibitors at all temperatures.

The following examples are given to more fully describe certain aspects of the invention set out above and are given primarily for the purpose of illustration;

and the invention, in its broader aspects, is not to be construed as limited thereto.

EXAMPLE I Seven samples (A through H) of 15 percent hydrochloric acid and five samples (I through M) of percent hydrochloric acid are prepared as follows:

Samples A and B (15% HCl) 2.0% by volume I-IAl-SO (Halliburton brand acid corrosion inhibitor) Samples C and D (15% I-ICl) 2.0% by volume Dowell-AllO (Dow Chemical Company acid corrosion inhibitor) Samples E and F (15% I-ICl) 2.0% by volume Wellaid-2l l (AMOCO brand acid corrosion inhibitor) Samples G through M contain 2.0% by volume Blend-57 (Halliburton brand acid corrosion inhibitor) Samples G and H are 15% HCl and Samples 1 through M are 30% BC].

Two thousand ppm cuprous iodide by weight of treating acid-acid corrosion inhibitor mixture is added to Samples A, C, E, and G and 5,000; 7,000; 9,000; and 11,000 ppm cuprous iodide by weight of said mixture are added to Samples 1, J, K, and L respectively. A coupon of API Type N-80 steel is placed in sufficient acid to produce an acid volume-to-surface area ratio of 90 cc/inF. The samples are heated to 300F and left for 2 hours at which time the corrosion in lbs/ft. is measured and recorded.

Table l, below, shows the intensifying effect of various concentrations of cuprous iodide in ppm on three types of acid corrosion inhibitors in 15 percent hydrochloric acid and on one type of acid corrosion inhibitor in 30 percent hydrochloric acid at temperatures of 300F, clearly illustrating the invention.

TABLE I Inhibitor Concentration: 2.0%

Test Temperature 300F Test Time 2 hours Metal Type N- Acid HCl Acid Volume Surface Area Ratio: cc/in.

5 Concen- Concen- Sample Inhibitor tration tration Corrosion HCI Cu l, lbJft.

(m A HAI-SO 15% 2,000 0.007

B HAl-SO 15% 0.062 c Dowell-Al to 15% 2,000 0.014 D Dowell-Al 10 15% 0 0.054 E Wellaid-Zl 1 15% 2,000 0.019 F Wellaid-21 1 15% 0 0.077 G Blend-57 15% 2,000 0.009 H Blend-57 15% 0 0.027 1 Blend-57 30% 5,000 0.095 J Blend-57 30% 7,000 0.062 K Blend-57 30% 9,000 0.053 L Blend-57 30% 1 1,000 0.040 M Blend-57 30% 0 0.77

EXAMPLE II Five samples, A through E, of 15% HCl with 0.25 percent by volume acid corrosion inhibitor are prepared. An A?! Type J-55 metal coupon is placed in each sample. Each sample contains sufficient treating acid-acid corrosion inhibitor mixture to achieve an acid volume-metal surface area ratio of 25 cc/in. Various amounts of cuprous iodide are placed in the five samples, and the samples are heated to 200F. The coupons are removed after 17 hours, and the corrosion loss is measured in lbs./ft. The results in Table 11, below, indicate the combination of cuprous iodide with said mixture forms an effective acid corrosion inhibitor intensitier at low concentrations over long periods of time.

TABLE 11 Test Temperature 200F.

Test Time 17 hours Metal Type J-SS (APl) Acid l5% HCI Acid Volume Surface Area Ratio: 25 cc/in.

Sample Inhibitor Concentration Corrosion HAl-SO c11 1, (ppm) lbs/ft. A 0.25% None 0.090 B 0.25% 25 0.029 C 0.25% 50 0.01 l D 0.25% 100 0.008 E 0.25% 150 0.006

EXAMPLE Ill Four samples (A, B, C, and D) of 15% hydrochloric acid containing 2.0% Blend-57 acid corrosion inhibitor are prepared and heated to 400F.

Sample A contains 12,500 ppm cuprous iodide.

Sample B contains 15,000 ppm cuprous iodide.

Sample C contains sufficient cuprous oxide and potassium iodide to produce 15,000 ppm cuprous iodide.

Sample D, being the control, contains no acid inhibitor intensifier.

An API Type N-80 metal coupon is placed in each sample prior to heating with sufficient acid present to insure an acid volume-surface area ratio of about 90 cc/inF. The coupons are removed after 2 hours and the corrosion is measured in lbs./ft.

Table III, below, shows the addition of cuprous iodide to the acid corrosion inhibitor-treating acid mixture reduces acid corrosion to a generally acceptable rate even at high temperatures.

TABLE III Inhibitor Blend-57 Test Temperature 400F Metal Type N-80 (API) Acid 15% HCI Test Time 2 hours Acid Volume-Surface Area Ratio: 90cc/in.

Sumplc Concentration Corrosion Cu,l, (ppm) lbs./ft. A l2.500 0.064

B 15,000 0.062 C 15,000 (formed in situ) 0.077 D None Coupon dissolved EXAMPLE IV Eight samples (A through H) of 15 percent hydrochloric acid with 2.0 percent by volume concentration of Blend-57 acid corrosion inhibitor are prepared and heated to 350F.

Sample A is treated with 10,000 ppm cuprous iodide.

Sample B is treated with exact quantities of cuprous oxide and potassium iodide to produce 10,000 ppm cuprous iodide in situ.

Sample C is treated with sufficient cuprous oxide and potassium iodide to produce 10,000 ppm cuprous iodide in situ, plus a 5 percent excess of potassium iodide.

Sample D is treated with sufficient cuprous oxide and potassium iodide to produce 10,000 ppm cuprous iodide in situ, plus a 10 percent excess of potassium iodide.

Sample E is treated with sufficient cuprous oxide and potassium iodide to produce 10,000 ppm cuprous iodide in situ, plus a 15 percent excess of potassium iodide.

Sample F is treated with 12,000 ppm potassium iodide.

Sample G is treated with 6,500 ppm cuprous chloride.

Sample H is treated with 9,375 ppm cuprous oxide.

A coupon of A?! Type N-SO metal is placed in each sample prior to heating. The coupons are removed after 2 hours, and the amount of corrosion in lbs./ft. is determined.

It is seen from the data recorded in Table IV, below, that a slight excess of from about 5 percent to about 15 percent by weight of I ions will improve the effect of the cuprous iodide on the acid corrosion inhibitor treating acid mixture. The improvement of cuprous iodide added as a compound and formed in situ over other additives (Kl, CuCl and Cu O) is also shown.

TABLE IV lnhibitor 2.0% Blend-57 Test Temperature 350F Metal Type N- (API) Acid 15% HCl Test Time 2 hours Acid Volume-Surface Area Ratio: cc/in.

12,500 ppm cuprous iodide (4,175 ppm Cu+ ion).

EXAMPLE V Fourteen samples (1 to 14) of 15 percent hydrochloric acid are prepared. Various concentrations of Blend- 57 and HAl-SO acid. corrosion inhibitors are added to the samples along with various concentrations of cuprous iodide. A coupon of AP! Type N-80 metal is placed in each sample, and the samples are heated to 300F. The amount of corrosion in lbs/ft? is measured to determine the effect of various concentrations of cuprous iodide with various concentrations of inhibitor. It is observed, as shown in Table V, below, that a euprous iodide concentration of about 2,000 ppm is effective to produce satisfactory results in the presence of only about 0.3 percent by volume of Blend-57 and that only about 250 ppm cuprous iodide will produce satisfactory results with a 2.0 percent by volume concentration of HAI-50 at temperatures of about 300F.

TABLE V Test Temperature 300F Metal Type N-80 (API) Acid 15% HCI Test Time 2 hours Acid Volume-Surface Area Ratio: 90 cc/in.

Sample Inhibitor Concentration Corrosion Cu I (ppm) lbsJtt. 1 None 2,000 1 .5 2 0.1% Blend-57 2,000 1.24 3 0.3% Blend-57 2,000 0.019 4 0.5% Blend-57 2,000 0.017 5 1.0% Blend-57 2,000 0.019 6 1.5% Blend-57 2,000 0.020 7 2.0% Blend-57 2,000 0.009 8 2.0% Blend- 57 0 0.027 9 2.0% I-IAl-50 0 0.062 10 2.0% l-IAI-50 250 0.048 11 2.0% HAI-SO 500 0.029 12 2.0% I-IAI-SO 1,000 0.010 13 2.0% I-IAI-SO 1,500 0.010 14 2.0% HAI-SO 2,000 0.007

EXAMPLE VI Seven samples (1 through 7) of 15 percent. hydrochloric acid are prepared. Varying amounts of cuprous iodide are added to six of the samples, and an API Type J-55 steel coupon is placed in each acid solution and the solutions are heated to 150F. After 2 hours the coupon is then removed from the acid and weighed to determine the corrosion loss in pounds per square foot. The results in Table VI, below, indicate cuprous iodide may operate as an acid corrosion inhibitor at low temperatures when the corrosion conditions are not severe.

TABLE VI Test Temperature 150F Metal Type J-55 steel (API) Acid 15% BC] Test Time 2 hours Metal-Acid Ratio 25 cc/in. Sample Concentration Corrosion Cu l (ppm) lbsJtt. l 0 0.037 2 250 0.012 3 500 0.009 4 1,000 0.008 5 1,500 0.008 6 2,500 0.007 7 3,000 0.007

EXAMPLE VII Eight test samples are prepared using various treating acids and mixtures thereof as corrodents and various nitrogen compounds and acetylenic compounds as acid corrosion inhibitors. Five hundred ppm cuprous iodide is added to each sample. An API Type N-80 metal coupon is placed in each sample solution and each sample is heated to 200F. After 6 hours the coupon is removed and weighed to determine the acid corrosion loss in lbs./ft. Table VII, below, indicates cuprous iodide will form an efiective inhibited treating acid when combined with an acid corrosion inhibitor and hydrochloric, sulfuric, and acetic acids and mixtures of hydrochloric acid with acetic acid and hydrofluoric acid. Said table also indicates that an effective inhibited treating acid is formed by the addition of cuprous iodide to a treating acid and various acetylenic compounds and nitrogen compounds.

TABLE VII Test Temperature 200F Test Time 6 hours Metal Type N- (API) Corrosion-lbsJfl. 500 ppm Sample Inhibitor Acid No C11 1, Cu,1, 1 0.2% Armohib-3l 10% H 50 0.070 0.021

(nitrogen base acid corrosion inhibitor) 2 0.1% MSA Inhibitor 10% 0.0016 0.0014

(nitrogen base CH COOH acid corrosion inhibitor) 3 0.2% HAI-SO 15% HCl-10% 0.010 0.005

acetic 4 0.2% I-IAI-50 12% I-ICl-3% I-IF 0.019 0.004 5 0.3% propargyl 15% l-lCl 0.016 0.010

alcohol (100% active) 6 0.3% ethyl 15% HQ 0.379 0.044

octynol 7 0.3% alkyl 15% PIC] 0.031 0.006

pyridines 8 0.3% rosin 15% BC] 0.036 0.006

amine EXAMPLE VIII Twenty-two test samples of 15 percent hydrochloric acid are prepared. The samples are treated with 2.0% Blend-57 acid corrosion inhibitor. Twenty-one of the 22 samples are treated with 7,000 ppm of various compounds of iodine and copper. An API Type N-80 steel coupon is then placed in each sample and each sample is heated to 350F. After 2 hours the coupons are removed and tested for corrosion loss. Table VIII, below, indicates cuprous iodide forms an effective inhibited treating acid when added to a treating acid and an acetylenic and nitrogen acid corrosion inhibitors, and that cuprous iodide provides an improvement which is clearly better than that provided by other compounds of iodine or copper.

TABLE VIII Test Temperature 350F Test Time 2 hours Type Metal N-80 (API) Acid 15% I-ICl Metal-Acid Ratio cc/in. Inhibitor Iodine or Copper Corrosion Containing Compound lbs/ti. 2.0% Blend-57 None 1.5 2.0% Blend-57 7,000 ppm Cu,l, 0.013 2.0% Blend-57 7,000 ppm Fel, 0.182 2.0% Blend-57 7,000 ppm Csl 0.202 2.0% Blend-S7 7,000 ppm Cu Br 0.132 2.0% Blend-57 7,000 ppm Mn], 0.184 2.0% Blend-57 7,000 ppm Bi(IO 0.097 2.0% Blend-57 7,000 ppm 2101;, 0.196 2.0% Blend-57 7,000 ppm PbI 0.196 2.0% Blend-57 7,000 ppm B312 0.077 2.0% Blend-57 7,000 ppm iodoform 0.082 2.0% Blend-S7 7,000 ppm iodopropane 0.236 2.0% Blend-57 7,000 ppm iodomethane 0.320 2.0% Blend-57 7,000 ppm iodophenol 0.160 2.0% Blend-57 7,000 ppm Bil5 0.175 2.0% Blend-57 7,000 ppm l-iodonapthalene 0.240 2.0% Blend-57 7,000 ppm Z-iodopropane 0.200 2.0% Blend-57 7,000. ppm lithium iodide 0.218 2.0% Blend-57 7,000 ppm cupric sulfide 0.226 2.0% Blend-57 7,000 ppm cuprous sulfide 0.241 2.0% Blend-57 7,000 ppm stannous iodide V 0.136 2.0% Blend-57 7,000 ppm l-iodo- Z-methylpropane 0.279

EXAMPLE 1x Five samples (AE) are prepared using percent hydrochloric acid and 2 percent by volume Blend-57 acid corrosion inhibitor.

Sample A contains no cuprous iodide.

Sample B contains 3,000 ppm cuprous iodide.

Sample C contains 5,000 ppm cuprous iodide.

Sample D contains 7,000 ppm cuprous iodide.

Sample E contains 9,000 ppm cuprous iodide.

A coupon of AM Type N-80 steel is placed in each sample such that the surface area to acid volume ratio in each sample is about 90 cc/in. The samples are heated to 300F where the temperature is maintained for 12 hours. The corrosion loss to the coupon in samples A and B is measured after 2 hours, 6 hours, and 12 hours. The corrosion loss to the coupons in samples C, D and E is measured after 12 hours. The corrosion loss figures in Table IX, below, indicate the improvement in corrosion inhibition of the inhibited treating acid over an acid-acid corrosion inhibitor mixture. Said figures futher indicate that the inhibited treating acid provides additional contact time between the corrodent and the metal surface than was available with the acid-acid corrosion inhibitor mixture and that the useful contact time may be increased by increasing the cuprous iodide concentration in the inhibited treating acid.

TABLE IX Temperature 300F Time 12 hours Acid 15% HCl Inhibitor Blend-57 Amount Corrosion loss lbs/ft. Sample Cu l 2 hours 6 hours 12 hours in ppm A 0 0.027 1 .5 Coupon dissolved H 3.000 0.008 0.032 0.047 C 5,000 0.030 D 7,000 0.028 E 9,000 0.026

It is clear, then, that the inhibited treating acid herein described may be useful wherever ferrous metal is sought to be protected from the corrosive effects of treating acids at high temperatures. Such uses may include acidizing of subterranean formations such as oil, gas, and water wells, cleaning industrial machinery, pickling steel in acid and others. It will be apparent that many widely different uses may be made of the method of the present invention without departing from the spirit and scope thereof and, therefore, it is not intended to be limited except as indicated in the appended claims.

We claim:

I. An inhibited treating acid consisting essentially of a treating acid selected from the group consisting of hydrochloric acid, sulfuric acid, mixtures of hydrochloric acid and acetic acid, hydrofluoric acid and hydrochloric acid, sulfuric acid and acetic acid, sulfuric acid and hydrofluoric acid, and mixtures thereof,

cuprous iodide present in a concentration of from about 25 ppm by weight of said treating acid to about 25,000 ppm by weight of said treating acid, and

an acid corrosion inhibitor selected from the group consisting of acetylenic alcohols and mixtures thereof and mixtures of organic nitrogen compounds and acetylenic alcohols.

2. The inhibited treating acid of claim 1 wherein said acid corrosion inhibitor is present in a concentration of from about 0.1 percent to about 2.5 percent by volume of said treating acid.

3. The inhibited treating acid of claim 1 wherein said treating acid is present in strengths of from about pH 6.5 to about 35 percent by weight of treating acid in water.

4. The inhibited treating acid of claim 1 wherein said acid corrosion inhibitor is selected from said acetylenic alcohols and mixtures thereof.

5. The method of protecting a ferrous metal surface against acid corrosion which comprises the step of:

contacting said surface with an inhibited treating acid consisting essentially of:

a treating acid selected from the group consisting of hydrochloric acid, sulfuric acid, mixtures of hydrochloric acid and acetic acid, hydrofluoric acid and hydrochloric acid, sulfuric acid and acetic acid, sulfuric acid and hydrofluoric acid, and mixtures thereof;

an acid corrosion inhibitor selected from the group consisting of acetylenic alcohols and mixtures thereof, and mixtures of organic nitrogen compounds and acetylenic alcohols; and

cuprous iodide present in a concentration in the range of about 25 ppm by weight of treating acid to about 25,000 ppm by weight of treating acid wherein said contacting of said surface is conducted at temperatures of up to about 450F.

6. The method of claim 5 wherein said treating acid is present in strengths of from about pH 6.5 to about 35% by weight of treating acid in water.

7. The method of claim 5 wherein said acid corrosion inhibitor is present in a concentration of from about 0.1 percent to about 2.5 percent by volume of treating acid.

8. The method of protecting a ferrous metal surface against acid corrosion which comprises the steps of:

contacting said surface with an inhibited treating acid consisting essentially of a treating acid selected from the group consisting of hydrochloric acid, sulfuric acid, mixtures of hydrochloric acid and acetic acid, hydrofluoric acid and hydrochloric acid, sulfuric acid and acetic acid, sulfuric acid and hydrofluoric acid, and mixtures thereof a solution prepared by combining an acid soluble salt of iodine and an acid soluble salt of copper, and

an acid corrosion inhibitor selected from the group consisting of acetylenic alcohols and mixtures thereof and mixtures of organic nitrogen compounds and acetylenic alcohols;

and allowing said salts to form cuprous iodide in a concentration in the range of about 25 ppm by weight of treating acid to about 25 ,000 ppm by weight of treating acid.

wherein said contacting of said surface is conducted at temperatures of up to about 450F.

9. The method of inhibiting acid corrosion of ferrous metal surfaces at temperatures below about F, which comprises the steps of:

contacting a ferrous metal surface with an inhibited treating acid consisting essentially of:

a solution prepared by adding an acid soluble salt of iodine and an acid soluble salt of copper to an acid selected from the group consisting of hydrochloric acid, sulfuric acid, mixtures of hydrochloric acid and acetic acid, hydrofluoric acid and hydrochloric acid, sulfuric acid and acetic acid, sulfuric acid and hydrofluoric acid, and mixtures thereof; and

allowing said salts to form cuprous iodide, wherein said cuprous iodide is allowed to form in concentrations of from about 50 ppm to about 3,000 ppm by weight of acid,

and further, wherein there is utilized an excess of from about 5 percent to about percent by weight of said acid soluble salt of iodine.

10. The method of claim 9 wherein said acid soluble salt of iodine is potassium iodide.

11. The method of claim 9 wherein said acid soluble salt of copper is selected from the group consisting of cupric sulfate, cuprous oxide, cuprous chloride and cupric chloride.

12. The method of claim 9 wherein said acid is present in a strength of from about pH 6.5 to about 35 percent by weight of acid in water.

13. The method of protecting a ferrous metal surface against acid corrosion which comprises the steps of:

contacting said surface with an inhibited treating acid consisting essentially of a treating acid selected from the group consisting of hydrochloric acid, sulfuric acid, mixtures of hydrochloric acid and acetic acid, hydrofluoric acid and hydrochloric acid, sulfuric acid and acetic acid, sulfuric acid and hydrofluoric acid, and mixtures thereof,

a solution prepared by combining an acid soluble salt of iodine, and an acid soluble salt of copper, wherein there is utilized an excess of from about 5 percent to about 15 percent by weight of said acid soluble salt of iodine, and

an acid corrosion inhibitor selected from the group consisting of acetylenic alcohols and mixtures thereof; mixtures of organic nitrogen compounds and acetylenic alcohols; and organic nitrogen compounds selected from mono, di, and tri-alkyl amines having from two to six carbon atoms in each alkyl moiety, six membered N-heterocyclic amines, alkyl pyridines having from one to five nuclear aJkyl substituents per pyridine moiety wherein said alkyl substituents have from one to 12 carbon atoms, rosin amines, and mixtures thereof,

and allowing said salts to form cuprous iodide in a concentration in the range of about 25 ppm by weight of treating acid to about 25,000 ppm by weight of treating acid,

wherein said contacting of said surface is conducted at temperatures of up to about 450F.

14. The method of claim 13 wherein said acid soluble salt of iodine is potassium iodide.

15. The method of claim 13 wherein said acid soluble salt of copper is selected from the group consisting of cupric sulfate, cuprous oxide, cuprous chloride and cupric chloride.

16. The method of claim 13 wherein said treating acid is present in a strength of from about pH 6.5 to about 35 percent by weight of acid in water.

17. The method of claim 13 wherein said acid corrosion inhibitor is present in a concentration of from about 0.1 percent to about 2.5 percent by volume of treating acid.

' UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,773,465 Dated November 20, 1973 Inventor) Bill R. Keeney and Joe W. Johnson, Jr.

It is certified that error appears in the above-identified, patent v and that said Letters Patent are hereby corrected as shown below:

In Column 3, lines 22 through 24: Delete the formula and. insert therefor the formula Signed and sealed this 23rd day of April 19714..

(SEAL) Attest:

EDWARD I LFLE CIIER,JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents Patent No.

UNITED sTATEs PATENT OFFICE CERTIFICATE OF CORRECTION 3,773,465 Dated November" 20, 1973 Inventofls) Bill R. Keeney and Joe W. Johnson, Jr. 2

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Column 3, lines 22 through 24 Delete the formula and insert therefor the formula R CEC 1 OH Signed and sealed this 23rd day of April 197M.

(SEAL) Attest:

C. MARSHALL DANN EDWARD M.FLETCHER,JR.

Commissioner of Patents Attssting Officer 

2. The inhibited treating acid of claim 1 wherein said acid corrosion inhibitor is present in a concentration of from about 0.1 percent to about 2.5 percent by volume of said treating acid.
 3. The inhibited treating acid of claim 1 wherein said treating acid is present in strengths of from about pH 6.5 to about 35 percent by weight of treating acid in water.
 4. The inhibited treating acid of claim 1 wherein said acid corrosion inhibitor is selected from said acetylenic alcohols and mixtures thereof.
 5. The method of protecting a ferrous metal surface against acid corrosion which comprises the step of: contacting said surface with an inhibited treating acid consisting essentially of: a treating acid selected from the group consisting of hydrochloric acid, sulfuric acid, mixtures of hydrochloric acid and acetic acid, hydrofluoric acid and hydrochloric acid, sulfuric acid and acetic acid, sulfuric acid and hydrofluoric acid, and mixtures thereof; an acid corrosion inhibitor selected from the group consisting of acetylenic alcohols and mixtures thereof, and mixtures of organic nitrogen compounds and acetylenic alcohols; and cuprous iodide present in a concentration in the range of about 25 ppm by weight of treating acid to about 25,000 ppm by weight of treating acid wherein said contacting of said surface is conducted at temperatures of up to about 450*F.
 6. The method of claim 5 wherein said treating acid is present in strengths of from about pH 6.5 to about 35% by weight of treating acid in water.
 7. The method of claim 5 wherein said acid corrosion inhibitor is present in a concentration of from about 0.1 percent to about 2.5 percent by volume of treating acid.
 8. The method of protecting a ferrous metal surface against acid corrosion which comprises the steps of: contacting said surface with an inhibited treating acid consisting essentially of a treating acid selected from the group consisting of hydrochloric acid, sulfuric acid, mixtures of hydrochloric acid and acetic acid, hydrofluoric acid and hydrochloric acid, sulfuric acid and acetic acid, sulfuric acid and hydrofluoric acid, and mixtures thereof a solution prepared by combining an acid soluble salt of iodine and an acid soluble salt of copper, and an acid corrosion inhibitor selected from the group consisting of acetylenic alcohols and mixtures thereof and mixtures of organic nitrogen compounds and acetylenic alcohols; and allowing said salts to form cuprous iodide in a concentration in the range of about 25 ppm by weight of treating acid to about 25,000 ppm by weight of treating acid. wherein said contacting of said surface is conducted at temperatures of up to about 450*F.
 9. The method of inhibiting acid corrosion of ferrous metal surfaces at temperatures below about 150*F, which comprises The steps of: contacting a ferrous metal surface with an inhibited treating acid consisting essentially of: a solution prepared by adding an acid soluble salt of iodine and an acid soluble salt of copper to an acid selected from the group consisting of hydrochloric acid, sulfuric acid, mixtures of hydrochloric acid and acetic acid, hydrofluoric acid and hydrochloric acid, sulfuric acid and acetic acid, sulfuric acid and hydrofluoric acid, and mixtures thereof; and allowing said salts to form cuprous iodide, wherein said cuprous iodide is allowed to form in concentrations of from about 50 ppm to about 3,000 ppm by weight of acid, and further, wherein there is utilized an excess of from about 5 percent to about 15 percent by weight of said acid soluble salt of iodine.
 10. The method of claim 9 wherein said acid soluble salt of iodine is potassium iodide.
 11. The method of claim 9 wherein said acid soluble salt of copper is selected from the group consisting of cupric sulfate, cuprous oxide, cuprous chloride and cupric chloride.
 12. The method of claim 9 wherein said acid is present in a strength of from about pH 6.5 to about 35 percent by weight of acid in water.
 13. The method of protecting a ferrous metal surface against acid corrosion which comprises the steps of: contacting said surface with an inhibited treating acid consisting essentially of a treating acid selected from the group consisting of hydrochloric acid, sulfuric acid, mixtures of hydrochloric acid and acetic acid, hydrofluoric acid and hydrochloric acid, sulfuric acid and acetic acid, sulfuric acid and hydrofluoric acid, and mixtures thereof, a solution prepared by combining an acid soluble salt of iodine, and an acid soluble salt of copper, wherein there is utilized an excess of from about 5 percent to about 15 percent by weight of said acid soluble salt of iodine, and an acid corrosion inhibitor selected from the group consisting of acetylenic alcohols and mixtures thereof; mixtures of organic nitrogen compounds and acetylenic alcohols; and organic nitrogen compounds selected from mono, di, and tri-alkyl amines having from two to six carbon atoms in each alkyl moiety, six membered N-heterocyclic amines, alkyl pyridines having from one to five nuclear alkyl substituents per pyridine moiety wherein said alkyl substituents have from one to 12 carbon atoms, rosin amines, and mixtures thereof, and allowing said salts to form cuprous iodide in a concentration in the range of about 25 ppm by weight of treating acid to about 25,000 ppm by weight of treating acid, wherein said contacting of said surface is conducted at temperatures of up to about 450*F.
 14. The method of claim 13 wherein said acid soluble salt of iodine is potassium iodide.
 15. The method of claim 13 wherein said acid soluble salt of copper is selected from the group consisting of cupric sulfate, cuprous oxide, cuprous chloride and cupric chloride.
 16. The method of claim 13 wherein said treating acid is present in a strength of from about pH 6.5 to about 35 percent by weight of acid in water.
 17. The method of claim 13 wherein said acid corrosion inhibitor is present in a concentration of from about 0.1 percent to about 2.5 percent by volume of treating acid. 